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Yeast RNA-Protein Interactions Generate Beer Haze.
Esben Due Yding1, Olivier Caille2, Yves Gosselin2
1Department of Food Science, University of Copenhagen, Rolighedsvej 26, Frederiksberg C DK-1958, Denmark.
Journal of Agricultural and Food Chemistry
|July 22, 2025
Summary
Brewer yeast RNA and protein Z interact electrostatically to form beer haze, a key visual characteristic in styles like New England IPA. This RNA-protein haze can be a novel brewing ingredient.
Area of Science:
- Food Science
- Biochemistry
- Brewing Science
Background:
- Beer haze is a desirable visual characteristic in various beer styles, including wheat beers and New England IPAs.
- Yeast-derived extracts, particularly those rich in RNA, can contribute to beer turbidity.
- Understanding the molecular mechanisms behind haze formation is crucial for controlling beer quality and developing new brewing ingredients.
Purpose of the Study:
- To investigate the molecular composition and formation mechanism of haze generated by yeast RNA in beer.
- To determine the role of RNA and beer proteins in haze formation.
- To explore the potential of RNA-protein complexes as novel haze contributors in brewing.
Main Methods:
- Addition of yeast RNA to different European lager beers to induce haze.
- Analysis of haze composition using Fourier-transform infrared (FT-IR) spectroscopy and SDS-PAGE.
- Treatment of haze with ribonuclease to assess the role of RNA.
- Investigation of haze formation under varying beer ionic strength and pH conditions.
Main Results:
- Yeast RNA addition generated haze composed of approximately 1 μm particles, linearly dependent on RNA concentration.
- FT-IR and SDS-PAGE confirmed the presence of RNA and beer protein Z in the haze.
- Haze formation required intact polymeric RNA chains and was disrupted by ribonuclease treatment.
- Haze levels decreased with increased ionic strength and as beer pH approached the isoelectric point (pI) of protein Z.
- Haze formation was attributed to electrostatic interactions between protein Z and RNA.
Conclusions:
- Beer haze can be formed by electrostatic interactions between yeast-derived RNA and beer protein Z.
- Intact RNA molecules are essential for the formation of this RNA-protein haze.
- The level of haze is influenced by beer's ionic strength and pH, specifically in relation to protein Z's pI.
- RNA-protein complexes represent a viable alternative or supplement to conventional haze-forming agents in brewing.
